1. Field of the Invention
The invention relates to lampholders for lamps having two parallel pins extending from an end to establish electrical contact, and more particularly to "medium bi-pin" fluorescent lampholders. Such lampholders are typically used in pairs, one for each end of a tubular lamp, and have a rigid molded plastic housing adapted to a mounting for a flat fluorescent fixture pan, the housing extending perpendicular to the fixture pan and receiving lamp pins by moving the lamp transversely to its longitudinal axis toward the pan, and inserting the pins through one or two slots in the lampholder.
These lampholders are usually made in "turn-lock" style, in which both pins are aligned to pass through one slot opening and the lamp is then rotated about its longitudinal axis to lock in place; and "straight-in" style which have a separate slot opening for each pin, and contacts that mechanically lock the pins in place as well as make electrical contact. A variety of housing styles and contacts for use in these styles have been devised over the years, and offer many different advantages and features.
2. Description of the Prior Art
Millions of lampholders of the turn-lock style are sold in the United States each year for residential and commercial use. As a result, many efforts to reduce cost and improve life or reliability have been made. U.S. Pat. No. 3,060,400 teaches a relatively complex contact for a turn-lock type lampholder; however, this contact is simple to install in a lampholder housing, and offers good isolation between movement of a lamp pin-contacting section and a connection wire pressure locking section. More recently, U.S. Pat. No. 3,337,837 teaches a different contact style which offers good wiping action of the contact but again is limited to the turn-lock construction.
For some purposes U-shape fluorescent tubes are preferred; and for these the turn-lock style cannot be used. A "straight-in" construction has been known for over 35 years, for example as disclosed in the U.S. Pat. to Burt, No. 2,280,747. More recently, many straight-in lampholder styles have been developed by different companies, such as the model 1615 made by Kulka Electric Corp. With these lampholders, the pins of a bi-pin fluorescent tube are pushed through parallel slots in the socket housing, and simultaneously engage contacts which lock them mechanically and complete the electrical circuit. In order to provide straight-line pin travel, with positive locking to prevent a tube from accidently falling from the socket, the known contacts for these sockets have been designed solely for straight-in lampholders. It has therefore been necessary to manufacture and stock separate contacts and lampholder housings for each type.